Water-soluble synthetic polymers (WSSPs) are found in many everyday products. What the consequences are when these plastics enter rivers, lakes and oceans is still largely unexplored. A team from the University of Bayreuth has now systematically investigated the effects on water fleas of the species Daphnia magna for the first time. The polymers selected for testing significantly alter the body size and reproduction of the animals in some cases. The research, published in Science of The Total Environment, shows that water-soluble polymers could have consequences for biodiversity and food chains in aquatic ecosystems that should not be underestimated.